Hard cal question Help please

An open box is to be made from a flat piece of material 7 inches long and 6 inches wide by cutting equal squares of length xfrom the corners and folding up the sides.
Write the volume Vof the box as a function of x. Leave it as a product of factors, do not multiply out the factors.

V=
If we write the domain of the box as an open interval in the form (a,b), then what is a=?
a=
and what is b=?
b=